Phase diagram and polarization of stable phases of (Ga_{1− x}In_x)₂O₃

Abstract

The full phase diagram of (Ga1− x In x )2O3 is obtained theoretically. The phases competing for the ground state are monoclinic β (low x), hexagonal (x ∼ 0.5), and bixbyite (large x). Three disconnected mixing regions interlace with two distinct phase-separation regions, and at x ∼ 0.5, the coexistence of hexagonal and β alloys with phase-separated binary components is expected. We also explore the permanent polarization of the phases, but none of them are polar. On the other hand, we find that ε-Ga2O3, which was stabilized in recent experiments, is pyroelectric with a large polarization and piezoelectric coupling, and could be used to produce high-density electron gases at interfaces.

The real structure of ε-Ga2O3 and its relation to κ-phase

“…In a recent reappraisal of Roy's work, Playford et al reported a total neutron diffraction investigation of these polymorphs. 12 According to first principle calculations, 9,13 the ε-phase is the second most stable polymorph after β. In the last years the growth of single-phase ε-Ga 2 O 3 thin films was demonstrated on commercial sapphire as well as other hexagonal or pseudo-hexagonal substrates.…”

Band Offsets at κ-([Al,In]xGa1–x)2O3/MgO Interfaces

“…Especially the frequency of reports on the orthorhombic κ-modification (sometimes also referred to as ε-Ga2O3) is rapidly increasing lately. Among the polymorphs of Ga2O3, this is the only crystalline phase expected to exhibit a spontaneous electrical polarization along its c-direction that is predicted to surpass even the one of GaN by one order of magnitude (23 µC/cm 2 ) [5][6][7][8] . The latter is the reason for the tremendously increasing interest in this phase.…”

Band alignment at surfaces and heterointerfaces ofAl2O3,Ga2O3,Hinuma1, Gake2, Oba3 2019Phys. Rev. Materials354210View full textAdd to dashboardCite

“…Sometimes a disordered structure with P6 3 mc space-group symmetry is labeled as ε-Ga 2 O 3 , which is comprised of domains of an ordered phase labeled κ-Ga 2 O 3 that is the same as the ordered orthorhombic ε-Ga 2 O 3 with Pna2 1 space-group symmetry [16]. These four phases are considered metastable [17,18], but the α- [19,20], γ - [21][22][23], and ε-Ga 2 O 3 [24][25][26] phases can be grown on various kinds of substrates. In particular, α-Ga 2 O 3 has been studied as a wide-gap semiconductor.…”